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Chymosin / ˈ k aɪ m ə s ɪ n / or rennin / ˈ r ɛ n ɪ n / is a protease found in rennet.It is an aspartic endopeptidase belonging to MEROPS A1 family. It is produced by newborn ruminant animals in the lining of the abomasum to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption.
Rennet has traditionally been used to separate milk into solid curds and liquid whey, used in the production of cheeses. Rennet from calves has become less common for this use, to the point that less than 5% of cheese in the United States is made using animal rennet today. [1] Most cheese is now made using chymosin derived from bacterial sources.
Κ-casein, or kappa casein, is a mammalian milk protein involved in several important physiological processes. Chymosin (found in rennet) splits K-casein into an insoluble peptide (para kappa-casein) and water-soluble glycomacropeptide (GMP).
The milk must be "ripened" before adding in the rennet. The term ripening means allowing the lactic acid bacteria (LAB) to turn lactose into lactic acid, which lowers the pH of the solution, greatly aiding in the coagulation of the milk. This is vital for the production of cheese curds that are later formed into cheddar.
The separate method differs from the usual one in that the purified milk is separated in order to obtain skimmed milk and cream, the mass fraction of fat in which is 50-55%. Fat-free tvorog is obtained from skimmed milk. In this case, acid-rennet coagulation of milk proteins is used to obtain a clot. Fat-free tvorog is cooled and mixed with cream.
The process is "characterized by a series of complex physical, chemical and microbiological changes" [3] that incorporates the agents of "bacteria and enzymes of the milk, lactic culture, rennet, lipases, added moulds or yeasts, and environmental contaminants". [2] The majority of cheese is ripened, except for fresh cheese. [2]
Acid-set or sour milk cheese is cheese that has been curdled (coagulated) by natural souring, often from lactic acid bacteria, or by the addition of acid. This type of cheese is technologically simple to produce. [1] When making soft acid-set cheese using bacteria, the coagulum results from production of lactic acid by the starter ...
The abomasum, also known as the maw, [1] rennet-bag, [1] or reed tripe, [1] is the fourth and final stomach compartment in ruminants. It secretes rennet , which is used in cheese creation. The word abomasum ( ab- "away from" + omasum " intestine of an ox ") is from Neo-Latin and it was first used in English in 1706.